lec 1 -2 nano technology.pptx

Nanotechnology  Nanotechnology The word "nano" comes from Greek word and means "dwarf'. A nanometer (nm) is a billionth of a meter (10-9 m) Nanotechnology refers to the branch of science and engineering devoted to designing, producing, and using structures, devices, and...

Nanotechnology  Nanotechnology The word "nano" comes from Greek word and means "dwarf'. A nanometer (nm) is a billionth of a meter (10-9 m) Nanotechnology refers to the branch of science and engineering devoted to designing, producing, and using structures, devices, and systems by manipulating atoms and molecules at nanoscale, where properties differ significantly from those at larger scale Nanoscience is indeed the study of phenomena at a scale that's smaller than the microscopic but larger than atomic scales The idea of nano technology was for first time introduced in 1959, by Richard Feynman a physicist at Caltech The term nanotechnology was first used in 1974 by late Norio Taniguchi.  Nanotechnology Nanotechnology encompasses the design, characterization, production, and application of structures, devices, and systems with controlled shapes and sizes at the nanometer scale. The field deals with the synthesis and use of materials that range from 1 to 100 nm. At the nano-scale, materials exhibit unique physical, chemical, and biological properties. These can be vastly different from the properties observed at larger scales, like bulk matter, or even at smaller scales, like individual atoms or molecules. This distinct behavior at the nano-scale opens up a abundance of opportunities for innovative applications and functionalities.  Visualizing the nano-scale is no easy task due to its extreme minuteness. A single is a billionth of a meter, or 10-9 of a meter. a scale that's beyond our everyday experience. Here are a few illustrative examples  There are 2,54,00,000 nanometers in an inch.  A sheet of newspaper is about 100,000 nanometers thick.  Comparison between Nano- size 103 Tennis Salt 10 Cell 10 5 ball 7 grain 104 10 10 8 6  Comparison between Nano- size Virus Protei Water 10 n1 2 1 0 10 - 1 DNA 6 7 Nano-particle  A Nano-particle is a minuscule entity, typically between 1 and 100 nanometers in size, that behaves as a complete unit regarding its transport and properties.  Nano-particle is a natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as agglomerate and where, for 50 per cent or more of the particles in the number size distribution , one or more external dimensions is in the size range 1 nm- 100 nm. Occurrence: Nano-particle exists in the natural world and is also created as a result of human activities.  Natural Existence: Nano-particles are not just a product of modern science; they've been around since the beginning. They can be found in natural systems, like volcanic ash, ocean spray, or even in some biological systems.  Anthropogenic Creation: Due to technological advancements, humans can now deliberately produce and manipulate Nano-particles for various applications. This can be through physical methods (like milling or attrition), chemical methods (like chemical vapor deposition), or biological processes.  Properties Three major physical properties of Nano-particle and all are interrelated: They are highly mobile in the free state. They have enormous specific surface areas. - Due to their tiny size, Nano-particles have a high surface-to-volume ratio, making them highly reactive or catalytically active compared to bulk materials They may exhibit what are known as quantum effects. - The properties of Nano-particles can differ significantly from those of their bulk counterparts. - Nano-particles can exhibit quantum effects that aren't observed in bulk materials. This can result in unique electronic, optical, and magnetic properties. - For example, gold Nano-particles can appear red or purple, while bulk gold is shiny gold. - Quantum dots, which are semiconductor Nano-particles, can fluoresce in a variety of colors when exposed to light, and this color can be tuned based on the size of the quantum dot  Manufacturing of nanomaterials Two main approaches are used in nano technology. In the bottom-up approach, materials and devises are built from molecular components and which assemble themselves chemically by principles of molecular recognition. In the top-down approach, nano objects are constructed from larger entities without atomic level control Bottom-Up Approach in Nanotechnology One of the primary mechanisms in this approach is self-assembly, where molecules organize themselves into structures based on their shape, charge, or other properties. This can be seen in nature, for example, in the way that DNA forms a double helix or proteins fold into specific shapes. Techniques and Examples: Chemical Synthesis: This involves creating complex molecules from simpler precursors, allowing for the design of specific functionalities or properties at the nano-scale. Molecular Electronics: Using organic molecules to create electronic components, potentially leading to smaller, more efficient devices. Dendrimers: These are repeatedly branched molecules that can be used for drug delivery, among other applications. Quantum Dots: Nano-scale semiconductor particles that have quantum mechanical properties. They can be created using a bottom-up approach and have applications in displays, solar cells, and biomedicine. Advantages: Precision: Molecules will naturally assemble in a consistent, repeatable way, leading to highly precise structures. Efficiency: The process often occurs spontaneously under the right conditions, requiring less external energy or intervention. Versatility: With the right molecular building blocks, a wide variety of structures can be produced. Challenges: While the bottom-up approach offers precision, scalability can be a challenge. It might not always be feasible to produce large quantities of a material or device using this method. Ensuring consistency and purity in the synthesized structures is crucial, especially if they are to be used in applications like medicine  TOP DOWN APPROACH The top-down approach starts with bulk materials and uses various techniques to extract or fabricate smaller structures or features from them without necessarily controlling formation at the atomic level. Techniques and Examples: Lithography: This is one of the most common techniques, especially in electronics manufacturing. Photolithography, for example, uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical on a substrate, which can then be etched to achieve nano-sized features. Electron Beam (e-beam) Lithography: Uses a focused beam of electrons to write custom patterns onto the surface of a semiconductor. Nano-imprint Lithography: This is a method of fabricating nanometer- scale patterns by pressing a mold into a substrate and solidifying the pattern. Etching: This can be either wet etching, using liquid chemicals, or dry etching, using ion beams or plasma. Milling: Atomic or ion milling techniques might be used to carve out specific structures from a solid piece. Advantages: Scalability: It often allows for the production of large quantities of nanostructures. Maturity: Many top-down processes have evolved from existing microfabrication methods and are thus relatively mature and well-understood. Integration: As many top-down techniques are derived from semiconductor manufacturing, they can be easily integrated into current microfabrication processes. Challenges: Limitations on Size: As we approach atomic scales, top-down methods may become less precise and reliable. Stress and Defects: High-energy processes used in top-down methods can introduce defects or stresses into the resulting structures. Waste Production: Material removal processes can result in more waste than additive processes like the bottom-up approach.  Nano-scale effects Materials reduced to nano-scale can show different properties compared to what they exhibit on a macroscale, enabling unique applications. The nanoscale effect refers to the unique physical and chemical properties that materials exhibit when they are reduced to the nanoscale, typically between 1 and 100 nanometers. At this scale, materials behave differently compared to their bulk counterparts due to factors such as increased surface area, quantum effects, and the dominance of surface forces Properties of materials are size-dependent in this scale range. Thus, when particle size is made to be nano scale properties such as melting point, fluorescence, electrical conductivity, magnetic permeability and chemical reactivity change as a function of size of the particle  Examples  For instance, opaque substances become transparent (Copper),  Stable materials turn combustible (Aluminum),  Solids turn into liquids at room temperature (Gold);  Insulators become conductors (Silicon).  A material such as Gold, which is chemically inert at normal scale, can serve as a potent chemical catalyst at nano scale.  Key Aspects of Nanoscale Effects: 1. Increased Surface Area-to-Volume Ratio: As materials are reduced to the nanoscale, the proportion of atoms on the surface increases relative to those inside. This increased surface area can significantly enhance the material's reactivity, making it more chemically active. 2. Quantum Effects: At the nanoscale, quantum mechanics begin to dominate the behavior of materials. Quantum confinement can affect the electronic properties, leading to phenomena such as discrete energy levels in semiconductors and changes in optical properties 3. Mechanical Properties: Nanomaterials can exhibit significantly different mechanical properties, such as increased strength, hardness, and elasticity. For instance, carbon nanotubes and graphene are known for their exceptional strength-to-weight ratios. 4. Optical Properties: Nanoparticles can display unique optical properties, such as localized surface plasmon resonance (LSPR) in metal nanoparticles, where they absorb and scatter light in a way that depends on their size, shape, and surrounding environment. This is utilized in applications like sensing and imaging. 5. Thermal Properties:  The thermal conductivity of materials can change at the nanoscale. For example, some nanomaterials may exhibit reduced thermal conductivity, which can be beneficial for thermoelectric applications 6. Magnetic Properties:  Magnetic nanoparticles can show superparamagnetism, where they become magnetized only in the presence of an external magnetic field and lose their magnetization when the field is removed. This is useful in data storage and medical imaging.  Nano-scale materials have far larger surface areas than similar masses of larger-scale Materials. As surface area per mass of a material increases, a greater amount of the material can come into contact with surrounding materials, thus affecting reactivity. Size of cube side Number of cubes Collective surface area 1.0 m 1 6 m2 0.1 m 1000 60 m2 0.01 m = 1 cm 106 = 1 million 600 m2 0.001 m = 1mm 109 = 1 billion 6000 m2 0.09 m= 1 nm 1027 6 x 109 = 6000 km2 Increase in surface area from 1 m3 to 1 nm3  Nano-scale gold Nano-scale gold illustrates the unique properties that occur at the nano- scale. Nano-scale gold particles are not the yellow color which we are familiar; nano-scale gold can appear red or purple. At the nano-scale, motion of golds electrons is confined. Because this movement is restricted, Gold nano-particles react differently with light compared to larger scale gold particle. Their size and optical properties can be put to practical use: nano scale gold particles selectively accumulate in tumors, where they can enable both precise imaging and targeted laser destruction of the tumor by means that avoid harming healthy cells.  Applications Medicine: Nano-particles are used for targeted drug delivery, where they can directly deliver drugs to diseased cells, reducing side effects. Agriculture: They can be used to deliver fertilizers and pesticides more efficiently, ensuring minimal wastage. Engineering: In electronics, Nano-particles can be used to develop smaller, faster, and more energy-efficient components. Catalysis: Their high reactivity makes them excellent candidates for catalytic applications, enhancing reaction rates. Environmental Remediation: Nano-particles can be engineered to remove pollutants or contaminants from air and water.